#!/bin/bash
#
# Developed by Fred Weinhaus 5/8/2008 .......... revised 4/3/2015
#
# ------------------------------------------------------------------------------
# 
# Licensing:
# 
# Copyright © Fred Weinhaus
# 
# My scripts are available free of charge for non-commercial use, ONLY.
# 
# For use of my scripts in commercial (for-profit) environments or 
# non-free applications, please contact me (Fred Weinhaus) for 
# licensing arrangements. My email address is fmw at alink dot net.
# 
# If you: 1) redistribute, 2) incorporate any of these scripts into other 
# free applications or 3) reprogram them in another scripting language, 
# then you must contact me for permission, especially if the result might 
# be used in a commercial or for-profit environment.
# 
# My scripts are also subject, in a subordinate manner, to the ImageMagick 
# license, which can be found at: http://www.imagemagick.org/script/license.php
# 
# ------------------------------------------------------------------------------
# 
####
#
# USAGE: tunnelize [-m mode] infile outfile
# USAGE: tunnelize [-h or -help]
#
# OPTIONS:
#
# -m      mode        mode of transform; mode=1 or 2; default=1
#
###
#
# NAME: TUNNELIZE 
# 
# PURPOSE: To create a tunnel-like effect on an image.
# 
# DESCRIPTION: TUNNELIZE creates a tunnel-like effect on an image 
# by swapping polar for cartesian coordinates.
# 
# OPTIONS: 
# 
# -m mode ... MODE is either 1 or 2. Mode=1 swaps angle for x and 
# radius for y. Mode=2 swaps radius for x and angle for y.
#
# NOTE: This script may run rather slowly as it uses -fx. A similar 
# effect to mode=1 can be achieved using -distort arc "360 90 size 0",
# where size is in the range of half one or the other dimensions of the 
# image or as large as the half diagonal of the image.
# 
# CAVEAT: No guarantee that this script will work on all platforms, 
# nor that trapping of inconsistent parameters is complete and 
# foolproof. Use At Your Own Risk. 
# 
######
#

# set default values
mode=1

# set directory for temporary files
dir="."    # suggestions are dir="." or dir="/tmp"

# set up functions to report Usage and Usage with Description
PROGNAME=`type $0 | awk '{print $3}'`  # search for executable on path
PROGDIR=`dirname $PROGNAME`            # extract directory of program
PROGNAME=`basename $PROGNAME`          # base name of program
usage1() 
	{
	echo >&2 ""
	echo >&2 "$PROGNAME:" "$@"
	sed >&2 -e '1,/^####/d;  /^###/g;  /^#/!q;  s/^#//;  s/^ //;  4,$p' "$PROGDIR/$PROGNAME"
	}
usage2() 
	{
	echo >&2 ""
	echo >&2 "$PROGNAME:" "$@"
	sed >&2 -e '1,/^####/d;  /^######/g;  /^#/!q;  s/^#*//;  s/^ //;  4,$p' "$PROGDIR/$PROGNAME"
	}


# function to report error messages
errMsg()
	{
	echo ""
	echo $1
	echo ""
	usage1
	exit 1
	}


# function to test for minus at start of value of second part of option 1 or 2
checkMinus()
	{
	test=`echo "$1" | grep -c '^-.*$'`   # returns 1 if match; 0 otherwise
    [ $test -eq 1 ] && errMsg "$errorMsg"
	}

# test for correct number of arguments and get values
if [ $# -eq 0 ]
	then
	# help information
   echo ""
   usage2
   exit 0
elif [ $# -gt 4 ]
	then
	errMsg "--- TOO MANY ARGUMENTS WERE PROVIDED ---"
else
	while [ $# -gt 0 ]
		do
			# get parameter values
			case "$1" in
		  -h|-help)    # help information
					   echo ""
					   usage2
					   exit 0
					   ;;
				-m)    # get mode
					   shift  # to get the next parameter - scale
					   # test if parameter starts with minus sign 
					   errorMsg="--- INVALID MODE SPECIFICATION ---"
					   checkMinus "$1"
					   mode="$1"
					   [ $mode -ne 1 -a $mode -ne 2 ] && errMsg "--- MODE=$mode MUST BE EITHER 1 OR 2 ---"
					   ;;
				 -)    # STDIN and end of arguments
					   break
					   ;;
				-*)    # any other - argument
					   errMsg "--- UNKNOWN OPTION ---"
					   ;;
		     	 *)    # end of arguments
					   break
					   ;;
			esac
			shift   # next option
	done
	#
	# get infile and outfile
	infile="$1"
	outfile="$2"
fi

# test that infile provided
[ "$infile" = "" ] && errMsg "NO INPUT FILE SPECIFIED"

# test that outfile provided
[ "$outfile" = "" ] && errMsg "NO OUTPUT FILE SPECIFIED"

# NOTE: testing with IM 6.6.0.10, 6.7.4.10, 6.7.6.10, 6.7.9.0, the results are not as sharp as the examples.

# test if image an ordinary, readable and non-zero size
if [ -f $infile -a -r $infile -a -s $infile ]
	then
	: 'Do Nothing'
else
	errMsg "--- FILE $infile DOES NOT EXIST OR IS NOT AN ORDINARY FILE, NOT READABLE OR HAS ZERO SIZE ---"
fi

# get parameters
w2=`convert $infile -format "%[fx:w/2]" info:`
h2=`convert $infile -format "%[fx:h/2]" info:`
r2=`convert $infile -format "%[fx:hypot(w/2,h/2)]" info:`
pi2=`convert xc: -format "%[fx:2*pi]" info:`

# process image
if [ $mode -eq 1 ]
	then
	convert "$infile" -monitor -fx "xx=(i-$w2); yy=(j-$h2); rr=hypot(xx,yy); aa=atan2(yy,xx); u.p{(aa+pi)*w/$pi2,rr*h/$r2}" "$outfile"
else
	convert "$infile" -monitor -fx "xx=(i-$w2); yy=(j-$h2); rr=hypot(xx,yy); aa=atan2(yy,xx); u.p{rr*w/$r2,(aa+pi)*h/$pi2}" "$outfile"
fi
exit 0
